"A 40kph speed area can significantly reduce the risk of death for pedestrians and cyclists if there is a collision," Mr Rattenbury said.

"For example a 10 km/h decrease in speed from 50 kph to 40 kph can reduce the risk of death by over 50 per cent.

"Slower speed environments are an important part of making our town centres safer for everyone to walk and cycle, and will have a minimal impact on drivers."

NRMA director Alan Evans says the motoring organisation is comfortable with the introduction of the permanent lower speed limits after the trial.

"The reality is that in many of those town centres you can not do more than 40 kph because of the traffic and people's mindfulness for pedestrians who are very prevalent in all those centres," he said.

However Mr Evans has warned the variety of speed limits across Canberra are confusing for motorists.

"There's no two ways about it people will get booked for exceeding 40 kph because they are confused, and its one of the things that the NRMA is campaigning on to try to make sure that we reduce the number of speed zones," he said.

"We've seen that come in to effect in NSW, we're seeing it have some effect in other states."

The announcement comes after a successful trial of the lower speed limits in Gungahlin and Woden.